Taysha Gene Therapies, Inc. (TSHA)

The company is a clinical-stage biotechnology company that develops AAV-based gene therapies for severe monogenic diseases of the central nervous system, in both rare and large patient populations. Its lead program, TSHA-102, is aimed at Rett syndrome, a rare neurodevelopmental disorder for which no approved disease-modifying therapy addresses the genetic root cause. The company draws on its management team's gene therapy development and commercialization experience, its manufacturing process, and a clinically and commercially proven AAV9 capsid.

TSHA-102 is a self-complementary, intrathecally delivered AAV9 gene transfer therapy designed as a one-time treatment that delivers a functional MECP2 gene to CNS cells. It uses the company's miRNA-Responsive Auto-Regulatory Element (miRARE) technology to regulate MeCP2 levels cell by cell and limit over- and under-expression. It is being studied in two Phase 1/2 REVEAL trials: an adolescent and adult trial in the United States and Canada, and a pediatric trial in the United States, Canada and the United Kingdom. Dosing of all 10 patients in Part A is complete. As of the February 17, 2025 data cutoff, there were no treatment-related serious adverse events or dose-limiting toxicities, and the company reported clinical improvements across multiple domains in the low-dose cohorts. Part B is the planned pivotal phase, and the company expects to report cohort data and an update on pivotal trial design in the first half of 2025. TSHA-102 has orphan drug, rare pediatric disease, Fast Track and RMAT designations from the FDA, orphan drug designation from the European Commission, and ILAP designation and CTA clearance in the U.K. The pipeline also includes preclinical programs: TSHA-113 for tauopathies, TSHA-106 for Angelman syndrome, and TSHA-114 for Fragile X syndrome. The company has deprioritized TSHA-105 (SLC13A5 deficiency), TSHA-118 (CLN1 disease) and TSHA-121 (CLN7), though it may revisit them or pursue partnerships.

The company targets patients with severe unmet medical needs and their caregivers. It cites more than 350,000 Rett syndrome patients worldwide and an estimated addressable population of 15,000 to 20,000 patients with typical Rett syndrome in the United States, European Union and United Kingdom. Other estimated populations include about 55,000 Angelman syndrome patients and 75,000 Fragile X syndrome patients in the United States and Europe.

On operations, the company holds a license from Abeona for CLN1 disease, for which it paid a $3.0 million upfront fee, and an in-licensed Angelman gene replacement construct from the University of North Carolina. It also has a research, collaboration and license agreement with UT Southwestern, under which it has no future milestone or royalty obligations beyond patent maintenance costs, and it transferred rights to certain indications back in December 2023. The FDA endorsed its intended GMP commercial manufacturing process in a CMC-focused Type D meeting in the fourth quarter of 2024. The company also established analytical comparability between clinical product and product from the final commercial process. Clinical trial material for TSHA-105 and TSHA-118 has been manufactured and released. Biogen and Ionis are mentioned as developers of a tau-targeting antisense oligonucleotide, the approach to which TSHA-113 is positioned as a one-time alternative.